System and method of data transmission in tension members of a fiber optical system

ABSTRACT

A system and method transmits graphic data received at varying frequencies at a fixed data rate. The frequency dependent data and associated data clock signal are received and the frequency dependent data is converted to frequency independent data. A ratio of a number of data clock cycles to a number of reference clock cycles is determined and transmitted. The frequency independent data and header data are transmitted, at a fixed rate, to a receiver, the fixed rate being a frequency greater than the frequency of the associated data clock signal. The received the frequency independent data is converted to frequency dependent data based upon the received determined ratio. The communication channel may include an optical fiber and a tension member wherein control data is transmitted along the tension member and graphic data is transmitted along the optical fiber.

FIELD OF THE PRESENT INVENTION

The present invention is directed to a method and system fortransmitting video data over a reduced number of digital visual and/orhigh definition media interface channels.

BACKGROUND OF THE PRESENT INVENTION

Digital Visual Interface and High-Definition Multimedia Interface arehigh speed serial interconnect standards to transmit graphical data froma source to some type of display. The standards operate over a largerange of data rates at very low differential voltage levels. Theinterface connection is limited to relatively short distance due to thecombination of high data rates (250 Mb/s to 1.65 Gb/s), low voltageswings (800 mV), reflections with the signal due to cable andconnectors, and compatibility issues between manufactures of thetransmitters and receivers.

One solution to the limitation of a relatively short distance is totransmit the Digital Visual Interface and/or High-Definition MultimediaInterface data over an optical fiber to increase the distance betweenthe source and display. This solution is realized by converting eachelectrical bit into an optical on/off state using a laser. The receiverat the other end of the fiber will use an optical detector andelectronics to convert the optical state into an electrical state.

However, this solution requires that each electrical channel be mapped1:1 to an optical fiber channel. In current graphic and videoapplications using Digital Visual Interface and/or High-DefinitionMultimedia Interface, three channels are utilized for graphic data, asingle channel for the clock, a single channel for upstream controldata, and a single channel for down stream control data.

FIG. 1 illustrates an example of this conventional system. In FIG. 1, adigital video source 20 is optically connected to a display device 30through an optical cable 10. This system requires numerous lasers,detectors, and fibers to establish a link between the source 20 anddisplay 30.

As illustrated in FIG. 2, the system of FIG. 1 requires numerous fibersthat add cost to the system. In FIG. 2, the optical cable 100 includesthree fiber (A, B, C) for graphic data, a single fiber (D) for theclock, a single fiber (E) for upstream control data, and a single fiber(F) for down stream control data. It is rioted that a fewer number offibers can be used, but in such configurations, the control data andreturn data are omitted from the system, thereby not complying with thespecification of Digital Visual Interface and/or High-DefinitionMultimedia Interface.

As noted above, optical fibers can be employed to transmit high volumeof information fast and reliably. The optical fibers include silicaoptical fibers, such as silica single-mode optical fibers, plasticoptical fibers, and other fibers. In particular, the plastic opticalfibers have a larger diameter than the silica single-mode optical fibersand are excellent in flexibility. From this viewpoint, the opticalcables, which employ plastic optical fibers has optical transmissionlines, are excellent in workability in end treatment and connectiontreatment of the optical fibers needed during installation, and inwiring. The optical cables are effective as a short distance trunk in abuilding after lead-in from a trunk cable, a branch cable, or a linecable for a LAN system.

The optical cables are usually configured to cover optical fibers andtensile strength reinforcing members (tension members) for avoidingelongation of the optical fibers due to tension with a sheath. Ingeneral, the optical fibers have a primary resin covering applied on asurface to prevent disturbance light from entering, to avoid damage dueto a mechanical external force, or for another reason. In the case ofoptical cables for communication, two or more optical fibers for bothinput and output are usually housed.

As noted above, some optical cables use added tension members within thesheath of the optical fiber assembly to provide greater tensilestiffness than the fiber used in the assembly. This is needed to helpreduce cable stress that will in time add additional loss in the fiber.Adding the extra tension member to the fiber assembly is commonly usedwith plastic optical fiber, but can be used with any fiber type that canbenefit from the added tensile strength.

With respect to another example of a conventional Digital VisualInterface and/or High-Definition Multimedia Interface system, the datatransfer system sends data back and forth from point A to point B;however, the data transfer system does not send the same amount of datain one direction as in the other direction. More specifically, in theconventional system, Point A could be sending data at 2 Gb/s to point B,but Point B is only sending 1 Mb/s of data to Point A. Typically, thistype of system would require two fiber channels, one for the high speeddownstream data and one for low speed upstream data, or a single modesystem that creates bi-directional data stream with two differentwavelengths, which adds additional circuitry.

Moreover, graphic applications operate at different clock rates fordifferent display resolutions. However in many data transferarchitectures it is beneficial to transmit the data at a fixed datarate. The problem in realizing this benefit is providing an adequateconversion of the variable rate data being received by the converter toa fixed data rate for actual transmission, and then a conversion of thefixed rate data back to a variable rate data without loss.

Lastly, Digital Visual Interface and/or High-Definition MultimediaInterface systems send graphic data and control data from the source tothe display, as well as, sending control data from the display to thesource. The graphic data, conventionally, is transmitted at a high datarate, while the control information is transmitted at a lower data rate.Since control data is flowing in both directions, the conventionalsystems have utilized bi-directional links. However, utilization ofbi-directional links adds an extra channel to the communication cable,thereby increasing its costs.

Therefore, it is desirable to provide a Digital Visual Interface and/orHigh-Definition Multimedia Interface system that provides a fixed rateof data transmission between a source and a display with a properconversion from a variable data rate to a fixed data rate and back to avariable data rate without loss of data.

Moreover, it is desirable to provide a Digital Visual Interface and/orHigh-Definition Multimedia Interface system that utilizes acommunication cable that provides bi-directional communication of thecontrol data without increasing the cable's cost.

Also, it is desirable to provide a Digital Visual Interface and/orHigh-Definition Multimedia Interface system that utilizes bi-directionalcommunication of the control data without increasing the cost of thesystem.

It is further desirable to provide a Digital Visual Interface and/orHigh-Definition Multimedia Interface system that utilizes a protocolwhich enables the reduction of channels needed in a communication cable.

SUMMARY OF THE PRESENT INVENTION

A first aspect of the present invention is a method for transmittingvarying frequency dependent data. The method receives frequencydependent data and associated data clock signal; converts the frequencydependent data to frequency independent data; determines a ratio of anumber of data clock cycles to a number of reference clock cycles;transmits the determined ratio; transmits, at a fixed rate, thefrequency independent data and header data to a receiver, the fixed ratebeing a frequency greater than the frequency of the associated dataclock signal; receives the frequency independent data and the determinedratio; and converts the frequency independent data to frequencydependent data based upon the received determined ratio.

A second aspect of the present invention is a method for transmittingvarying frequency dependent data. The method receives frequencydependent data having a pre-determined resolution format associatedtherewith; determines timing information from the received frequencydependent data; converts the received frequency dependent data tofrequency independent data; encodes the frequency independent data withthe determined timing information; transmits, at a fixed rate, thetiming information encoded frequency independent data to a receiver;receives the timing information encoded frequency independent data;extracts timing information from the timing information encodedfrequency independent data; and re-creates, based upon the extractedtiming information, frequency dependent data having the pre-determinedresolution associated therewith.

A third aspect of the present invention is a component for transmittinggraphical data generated by a graphical data source to a display device.The component includes a circuit to receive frequency dependent datafrom the graphical data source, having a resolution format and a dataclock frequency associated therewith, and to generate timing informationencoded frequency independent data therefrom; and a transmitter totransmit the timing information encoded frequency independent data at afixed rate to the display device.

A fourth aspect of the present invention is a system for transmittinggraphical data generated by a graphical data source to a display device.The system includes a communication channel; a first circuit to receivefrequency dependent data from the graphical data source, having aresolution format and a data clock frequency associated therewith, andto generate timing information encoded frequency independent datatherefrom; and a first transmitter, operatively connected to thecommunication channel, to transmit the timing information encodedfrequency independent data at a fixed rate; a second circuit,operatively connected to the communication channel, to receive thetiming information encoded frequency independent data; a third circuit,operatively connected to the second circuit, to extract timinginformation from the timing information encoded frequency independentdata and to re-create, based upon the extracted timing information,frequency dependent data having the pre-determined resolution associatedtherewith; and a second transmitter, operatively connected to the thirdcircuit, to transmit the frequency dependent data having thepre-determined resolution associated therewith to a display device.

Another aspect of the present invention is a method for transmittingvarying frequency dependent data. The method receives frequencydependent data and associated data clock signal; converts the frequencydependent data to frequency independent data; determines a ratio of anumber of data clock cycles to a number of reference clock cycles;transmits the determined ratio; transmits, at a fixed rate, frequencyindependent data and header data to a receiver, the fixed rate being afrequency less than the frequency of the associated data clock signal;receives the frequency independent data and the determined ratio; andconverts the frequency independent data to frequency dependent databased upon the received determined ratio.

Another aspect of the present invention is a system for transmittinggraphical data generated by a graphical data source to a display device.The system includes a communication channel having an optical fiber, asheath that surrounds the optical fiber to protect the optical fiber,and a tension member, located within the sheath, to provide tensilestiffness for the optical fiber; a first circuit to receive frequencydependent data from the graphical data source, having a predeterminedresolution format and a data clock frequency associated therewith, andto generate timing information and frequency independent data therefrom;and a first transmitter, operatively connected to the communicationchannel, to transmit the timing information along the tension member ata fixed rate and the frequency independent data along said optical fiberat a fixed rate; a second circuit, operatively connected to thecommunication channel, to receive the timing information and thefrequency independent data; a third circuit, operatively connected tothe second circuit, to extract, based upon the received timinginformation, frequency dependent data having the pre-determinedresolution associated therewith; and a second transmitter, operativelyconnected to the third circuit, to transmit the frequency dependent datahaving the pre-determined resolution associated therewith to a displaydevice.

Another aspect of the present invention is a point-to-pointcommunication cable. The point-to-point communication cable includes afirst interface having first and second communication members to providecommunication channels; a second interface having third and fourthcommunication members to provide communication channels; an opticalfiber, operatively connected to the first communication member of thefirst interface and the third communication member of the secondinterface, to provide a communication channel between the firstinterface and the second interface; a sheath, surrounding the opticalfiber, to protect said optical fiber; and a tension member, locatedwithin the sheath, to provide tensile stiffness for the optical fiber.The tension member, operatively connected to the second communicationmember of the first interface and the fourth communication member of thesecond interface, provides an electrical path between the firstinterface and the second interface.

Another aspect of the present invention is a communication system forproviding a transfer of data between two devices. The communicationsystem includes a point-to-point communication cable, the point-to-pointcommunication cable having a first interface having first and secondcommunication members to provide communication channels, a secondinterface having third and fourth communication members to providecommunication channels, an optical fiber that is operatively connectedto the first communication member of the first interface and the thirdcommunication member of the second interface to provide a communicationchannel between the first interface and the second interface, a sheaththat surrounds the optical fiber to protect said optical fiber, and afirst tension member, located within the sheath, to provide tensilestiffness for the optical fiber. The first tension member, operativelyconnected to the second communication member of the first interface andthe fourth communication member of the second interface, provides anelectrical path between the first interface and the second interface.The communication system further includes a current source, operativelyconnected to the second communication member, to provide a current ontothe first tension member; a switch, operatively connected to the fourthcommunication member, to modulate the current flowing through the firsttension member in response to data generated by a device connected tothe second interface; and a current monitor, operatively connected tothe second communication member, to monitor the modulated current and togenerate a data signal in response thereto.

Another aspect of the present invention is a method for transferringgraphical data from a source to a receiver. The method converts thefrequency dependent data to frequency independent data; transmits, froma source, at a fixed rate, clock data corresponding to a source pixelclock frequency associated with frequency dependent data; transmits,from the source, at a fixed rate, frequency independent data; receivesthe frequency independent data and the clock data at the receiver;stores the received frequency independent data in a memory; re-creates,at the receiver, based upon the received clock data, a pixel clocksignal having a frequency corresponding to the frequency of the sourcepixel clock frequency associated with frequency dependent data; andretrieves stored data from the memory using the re-created pixel clocksignal to generate frequency dependent data.

Another aspect of the present invention is a system for recreating fortransferring graphical data from a source to a receiver. The systemincludes a source of graphical data having a circuit to convert thefrequency dependent data, associated with a source pixel clockfrequency, to frequency independent data and a transmitter to transmit,at a fixed rate, clock data corresponding to a source pixel clockfrequency associated with frequency dependent data and to transmit, at afixed rate, frequency independent data; a receiver, communicativelyconnected to the source. The receiver includes a memory to storereceived frequency independent data; a digital clock synthesizer tore-create, based upon received clock data, a pixel clock signal having afrequency corresponding to the frequency of the source pixel clockfrequency associated with frequency dependent data; and a retrievalcircuit to retrieve the stored data from the memory using the re-createdpixel clock signal to generate frequency dependent data.

Another aspect of the present invention is a component for convertingfrequency independent data into frequency dependent data. The componentincludes a receiver to receive, at a fixed data rate, frequencyindependent data; a memory to store frequency independent data; adigital clock synthesizer to re-create a pixel clock signal having afrequency corresponding to a frequency of a source pixel clock frequencyassociated with frequency dependent data; and a retrieval circuit toretrieve the stored data from the memory using the re-created pixelclock signal to generate frequency dependent data.

Another aspect of the present invention is a system for transmittinggraphical data generated by a graphical data source to a display device.The system includes a communication channel; a first circuit to receivefrequency dependent data from the graphical data source, having apredetermined resolution format and a data clock frequency associatedtherewith, and to generate timing information and frequency independentdata therefrom; a first transmitter, operatively connected to thecommunication channel, to transmit the frequency independent data andtiming information at a fixed rate; a second circuit, operativelyconnected to the communication channel, to receive the timinginformation and the frequency independent data; a memory to store thefrequency independent data; a digital clock synthesizer to re-create,based upon received timing information, a pixel clock signal having afrequency corresponding to the frequency of the source pixel clockfrequency associated with frequency dependent data; a retrieval circuitto retrieve the stored data from the memory using the re-created pixelclock signal to generate frequency dependent data; and a secondtransmitter, operatively connected to said retrieval circuit, totransmit the frequency dependent data having the pre-determinedresolution associated therewith to a display device.

Another aspect of the present invention is a method for providing baseband-directional graphic data communication between a graphic datasource device and a display device. The method transmits display dataand control data from the graphic data source device to the displaydevice, over a first communication channel, during a data period andtransmits return data from the display device to the graphic data sourcedevice, over the first communication channel, during a non-data period.

Another aspect of the present invention is a method for providing baseband-directional graphic data communication between a graphic datasource device and a display device. The method transmits a start of dataperiod signal the graphic data source device to the display device overa first communication channel; transmits display data from the graphicdata source device to the display device over a first communicationchannel; transmits a end of data period signal the graphic data sourcedevice to the display device over a first communication channel; andtransmits, in response to the transmitted end of data period signal,return data from the display device to the graphic data source deviceover the first communication channel.

Another aspect of the present invention is a system for providing baseband-directional graphic data communication. The system includes agraphic data source device to generate display data and control data; adisplay device to display the display data and to generate return data;and a first communication channel, operatively connected to the graphicdata source device and the display device, to provide a communicationchannel therebetween. The graphic data source device includes a sourcetransmitter to transmit a start of data period signal, an end of dataperiod signal, and the display data; a source receiver to receive thereturn data; and a source switch, operatively connected to the sourcetransmitter, the source receiver, and the first communication channel.The source switch connects the source transmitter to the firstcommunication channel in response to the start of data period signal.The source switch connects the source receiver to the firstcommunication channel in response to the end of data period signal. Thedisplay device includes a display transmitter to transmit return data; adisplay receiver to receive the start of data period signal, the end ofdata period signal, and the display data; and a source switch,operatively connected to the display transmitter, the display receiver,and the first communication channel. The display switch connects thedisplay transmitter to the first communication channel in response tothe end of data period signal. The display switch connects the displayreceiver to the first communication channel in response to the start ofdata period signal.

Another aspect of the present invention is a system for transmittingdata between a remote central computing facility and a localworkstation. The system includes a remote central computing facilityincluding a plurality of primary processing devices; anelectrical/optical interface, operatively connected to the remotecentral computing facility, to provide an individual communicationchannel for each primary processing device; a plurality of communicationcables operatively connected to the electrical/optical interface; and alocal workstation operatively connected to a communication cable. Eachcommunication cable includes an optical fiber, a sheath, surrounding theoptical fiber, to protect the optical fiber, and a tension member,located within the sheath, to provide tensile stiffness for the opticalfiber. The electrical/optical interface includes a first circuit toreceive frequency dependent data from a graphical data source associatedwith a first primary processing device, having a predeterminedresolution format and a data clock frequency associated therewith, andto generate timing information and frequency independent data therefromand a first transmitter, operatively connected to a communicationchannel associated with the first primary processing device, totransmit, at a fixed rate, the timing information and the frequencyindependent data along the optical fiber. The local workstation includesa workstation interface; which includes a circuit, operatively connectedto the communication cable, to receive the timing information and thefrequency independent data, an extraction circuit, operatively connectedto the circuit, to extract, based upon the received timing information,frequency dependent data having the pre-determined resolution associatedtherewith, and a display circuit, operatively connected to saidextraction circuit, to transmit the frequency dependent data having thepredetermined resolution associated therewith to a display device.

Another aspect of the present invention is a system for transmittingdata between a remote central computing facility and a localworkstation. The system includes a remote central computing facilityincluding a plurality of primary processing devices; anelectrical/optical interface, operatively connected to the remotecentral computing facility, to provide an individual communicationchannel for each primary processing device; a plurality of communicationcables operatively connected to the electrical/optical interface; and alocal workstation operatively connected to a communication cable. Eachcommunication cable includes an optical fiber, a sheath, surrounding theoptical fiber, to protect the optical fiber, and a tension member,located within the sheath, to provide tensile stiffness for the opticalfiber. The electrical/optical interface includes a first circuit toreceive frequency dependent data from a graphical data source associatedwith a first primary processing device, having a predeterminedresolution format and a data clock frequency associated therewith, andto generate timing information and frequency independent data therefromand a first transmitter, operatively connected to a communicationchannel associated with the first primary processing device, totransmit, at a fixed rate, the timing information and the frequencyindependent data along the optical fiber. The local workstation includesa workstation interface; which includes a circuit, operatively connectedto the communication cable, to receive the timing information and thefrequency independent data, a memory to store the frequency independentdata, a digital clock synthesizer to re-create, based upon receivedtiming information, a pixel clock signal having a frequencycorresponding to the frequency of the source pixel clock frequencyassociated with frequency dependent data, a retrieval circuit toretrieve the stored data from the memory using the re-created pixelclock signal to generate frequency dependent data, and a displaycircuit, operatively connected to said extraction circuit, to transmitthe frequency dependent data having the pre-determined resolutionassociated therewith to a display device.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may take form in various components andarrangements of components, and in various steps and arrangements ofsteps. The drawings are only for purposes of illustrating a preferredembodiment and are not to be construed as limiting the presentinvention, wherein:

FIG. 1 illustrates a prior art digital video data source/display system;

FIG. 2 illustrates a prior art communication cable, used in FIG. 1, forcarrying digital video data;

FIG. 3 illustrates a digital video data source/display system accordingto the concepts of the present invention;

FIG. 4 illustrates a communication cable, used in FIG. 3, for carryingdigital video data according to the concepts of the present invention;

FIG. 5 is an illustration of line and frame timing for digital displaydata according to the concepts of the present invention;

FIG. 6 is a magnified illustration of the graphic data signal of FIG. 5;

FIG. 7 is a block diagram showing the protocol for producing timinginformation according to the concepts of the present invention;

FIG. 8 shows the architecture of a single data stream generated fromthree data streams according to the concepts of the present invention;

FIG. 9 is a block diagram illustrating a fixed rate optical extender fora digital video interface according to the concepts of the presentinvention;

FIG. 10 is a block diagram illustrating a second fixed rate opticalextender for a digital video interface according to the concepts of thepresent invention;

FIG. 11 is a graphical illustration of an optical communication systemaccording to the concepts of the present invention;

FIG. 12 illustrates a digital video data communication cable accordingto the concepts of the present invention;

FIG. 13 shows a graphical illustration of the transmission of digitalvideo data using current modulation according to the concepts of thepresent invention;

FIG. 14 shows a block diagram of the transmission of digital video datausing current modulation according to the concepts of the presentinvention;

FIG. 15 is a block diagram of a transmitter/receiver pair fortransmitting digital video data at a fixed rate according to theconcepts of the present invention;

FIG. 16 is a block diagram of the circuitry used to produce the protocolused in transmitting digital video data according to the concepts of thepresent invention;

FIG. 17 illustrates a block diagram of another transmitter/receiver pairfor transmitting digital video data at a fixed rate according to theconcepts of the present invention;

FIG. 18 illustrates the utilization of a memory element to convert thedata rate according to the concepts of the present invention;

FIGS. 19 and 20 illustrate memory storage conditions at a certain periodof time;

FIG. 21 illustrates a transmitter/receiver system between a data sourceand a display according to the concepts of the present invention;

FIG. 22 is a graphical illustration of a communication process between adata source and a display according to the concepts of the presentinvention;

FIG. 23 is a block diagram of the communication process of FIG. 22according to the concepts of the present invention; and

FIG. 24 is a block diagram illustrating the utilization of the conceptsof the present invention in a remote workstation environment.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention will be described in connection with preferredembodiments; however, it will be understood that there is no intent tolimit the present invention to the embodiments described herein. On thecontrary, the intent is to cover all alternatives, modifications, andequivalents as may be included within the spirit and scope of thepresent invention, as defined by the appended claims.

For a general understanding of the present invention, reference is madeto the drawings. In the drawings, like reference have been usedthroughout to designate identical or equivalent elements. It is alsonoted that the various drawings illustrating the present invention arenot drawn to scale and that certain regions have been purposely drawndisproportionately so that the features and concepts of the presentinvention could be properly illustrated.

As discussed above, it is desirable to reduce the number of channelsrequired to send Digital Visual Interface and/or High-DefinitionMultimedia Interface data. By reducing the number of channels, thenumber of fibers, detectors, lasers, and supporting integrated circuitswill also be reduced, thus providing a much more cost effective solutionwithout negatively impacting image or data quality.

An example of such a system is illustrated in FIG. 3. As illustrated inFIG. 3, a digital video source 20 is optically connected to a displaydevice 30 through an optical cable 11. This system does not requirenumerous lasers, detectors, and fibers to establish a link between thesource 20 and display 30 because, as illustrated in FIG. 4, the systemof FIG. 3 requires only a single channel (A) for graphic data and asingle channel (B) for the clock, upstream control data, and downstreamcontrol data. This can be done by designing a different configurationprotocol, as will be discussed in more detail below.

To reduce the number of Digital Visual Interface and/or High-DefinitionMultimedia Interface channels, extra bandwidth in the graphic datastream is utilized, and the various rates of Digital Visual Interfaceand/or High-Definition Multimedia Interface resolutions are converted toa fixed data rate.

In a preferred embodiment, the fixed data rate may be at a higher ratethan the highest Digital Visual Interface and/or High-DefinitionMultimedia Interface resolution. By establishing a fixed data rate atrate higher than the highest Digital Visual Interface and/orHigh-Definition Multimedia Interface resolution, multiple channels canbe converted to a single downstream channel and a single upstreamchannel.

Video Electronics Standards Association (VESA) is a standards body thatsets video and graphic resolutions standards. The VESA standards areused as the input and output formats for Digital Visual Interface and/orHigh-Definition Multimedia Interface transmitters and receivers. VESAstandards also define the amount of data active time and the amount ofblanking time (non data periods). The specification breaks down thedisplay data into line (one row of display data) and frame timing (thetime between the first row of data until that row receives new data). Agraphical illustration of the specification is shown in FIGS. 5 and 6wherein FIG. 5 shows line and frame timing for digital display data andFIG. 6 is a magnified illustration of the graphic data signal of FIG. 5.

As illustrated in FIG. 5, there is blanking time before and after theactive display data. There is also, as illustrated in FIG. 5, blankingtime before and after the very last row of display data. The next row ofdata will start again at the top of the screen indicating the nextvideo/graphics frame. To achieve the conversion of multiple channels toa single downstream channel and a single upstream channel, a system asillustrated in FIG. 7, initially takes measurements on the data goinginto the system (40) and produces timing information for inclusion inthe header information (42). The header information is multiplexed withgraphic data and idle codes (44) to produce a serial stream of data. Inthis system, idle codes are sent when graphic data or header data is notavailable to send. The sending of idle codes when graphic data or headerdata is not available to send enables the fixed rate data stream tocontinue to send information so as to keep the receiver locked. In otherwords, when very slow input data rates are used idle codes are sent tomaintain a constant data stream.

FIG. 8 shows the architecture of the data that takes three differentdata lines (plus control data) and puts them into a single data stream.The data in the serial stream is encoded to make data extraction at thereceiver possible without the use of a separate clock signal at thefixed rate frequency. More specifically, the receiver at the other endreads the header information and then recreates the necessary timinginformation as well as extracts the data back into the correctresolution format.

As discussed above and illustrated in FIG. 8, timing information,produced from the V_(SYNC), H_(SYNC), Data_(CLOCK), and Pixel_(CLOCK)signals, is placed in the header of each packet of data. The graphicdata from the various data channels (RED, GREEN, and BLUE) is encodedand multiplexed so as to follow the header information. If necessary,idle codes are sent when graphic data or header data is not available tosend so as to keep the receiver locked. As noted above, FIG. 9 is ablock diagram illustrating a fixed rate optical extender for a digitalvideo interface according to the concepts of the present invention.

As illustrated in FIG. 9, graphic data and timing signals are fed from agraphic card 200 to a variable rate to fixed rate digital visual and/orhigh-definition multimedia conversion component 210. The variable rateto fixed rate digital visual and/or high-definition multimediaconversion component 210 includes a Digital Visual Interface and/orHigh-Definition Multimedia Interface receiver 212. The Digital VisualInterface and/or High-Definition Multimedia Interface receiver 212measures the various timing signals to generate timing informationwherein the timing information is fed to a graphic encoder fixed ratecircuit 214. The graphic encoder fixed rate circuit 214 also receivesgraphic data from the graphic card 200.

The graphic encoder fixed rate circuit 214 produces the headerinformation from the timing information and encodes the multiplechannels of graphic data; e.g., red, green and blue channels of data.The graphic encoder fixed rate circuit 214 further transmits the headerinformation with the graphic data and the appropriate idle codes, whennecessary, to the serializer 216. The serializer 216 multiplexesinformation to create a serial data stream having a fixed data rate.

The serial data stream having a fixed data rate is converted to a streamof lights pulses by VCSEL Driver 220 and VCSEL 230. The light pulses arefed to an interface block 260 to be transmitted over an optical fiber incable 400 so as to be eventually displayed on a display device 300.

At the display device end, an interface block 370 receives the lightpulses from the optical fiber in cable 400. The light pulses areconverted to electrical signals by PIN 340, TIA 330, and limitedamplifier 320. The fixed data rate electrical data stream isde-serialized by de-serializer 316. The deserialized data is decoded bygraphic decoder fixed rate circuit 314 to produce graphic data andtiming information. The timing information is converted into timingsignals by a Digital Visual Interface and/or High-Definition MultimediaInterface transmitter 312. The timing signals and the decoded graphicdata are fed to a display device 300 for proper displaying of the imageor information.

Control data from the monitor 300 is fed to graphic decoder fixed ratecircuit 314 so as to be transmitted to the data source. The control datais converted to a stream of lights pulses by LED Driver 320 and LEDsource 330. The light pulses associated with the control data are fed tointerface block 370 to be transmitted over an optical fiber in cable 400so as to be eventually used by the graphic encoder fixed rate circuit214. The light pulses associated with the control data are converted toelectrical signals by LED detector 250 and TIA 240.

FIG. 10 is another block diagram illustrating a fixed rate opticalextender for a digital video interface according to the concepts of thepresent invention. As illustrated in FIG. 10, a Digital Visual Interfaceand/or High-Definition Multimedia Interface 510 generates graphic dataand timing information to be fed to a Digital Visual Interface and/orHigh-Definition Multimedia Interface receiver 520. The Digital VisualInterface and/or High-Definition Multimedia Interface receiver 520measures the various timing signals to generate timing informationwherein the timing information is fed to a programmable gate array 550.

The programmable gate array 550 produces the header information from thetiming information and encodes the multiple channels of graphic data;e.g., red, green and blue channels of data. The programmable gate array550 further transmits the header information with the graphic data andthe appropriate idle codes, when necessary, to a digital to opticalconverter 560. The digital to optical converter 560 converts the data toa stream of lights pulses. The light pulses are fed to an opticaltransceiver 570 to be transmitted over an optical fiber in cable 400.

At the display device end, an optical transceiver 670 receives the lightpulses from the optical fiber in cable 400. The light pulses areconverted to electrical signals by optical to digital converter 660. Thefixed data rate electrical data stream is decoded by programmable gatearray 650 to produce graphic data and timing information. The timinginformation is converted into timing signals by a Digital VisualInterface and/or High-Definition Multimedia Interface transmitter 620.The timing signals and the decoded graphic data are fed to a DigitalVisual Interface and/or High-Definition Multimedia Interface 610.

As noted above, with respect to a conventional Digital Visual Interfaceand/or High-Definition Multimedia Interface system, the data transfersystem sends data back and forth from point A to point B; however, thedata transfer system does not send the same amount of data in onedirection as in the other direction. More specifically, in theconventional system, Point A could be sending data at 2 Gb/s to point B,but Point B is only sending 1 Mb/s of data to Point A. Typically, thistype of system would require two fiber channels, one for the high speeddownstream data and one for low speed upstream data, or a single modesystem that creates bi-directional data stream with two differentwavelengths, which adds additional circuitry.

To avoid the above-noted problems, as illustrated in FIG. 11, a solutionmay be to use an optical fiber to send the high rate data to Point Bfrom Point A, but use an electrical signal caring medium for the datatransfer from Point B to Point A. For example, as illustrated in FIG.12, a fiber assembly may contain both optical fibers (r1, r2, r3, andr4) for high data rate signals and a tension member(s) (T1 and T2) thatare designed with a low resistance material. The tension member(s) (T1and T2) can be used to carry the lower data rate electrical signals.

There are various ways that the electrical signal could be constructedon the tension member(s) (T1 and T2). The tension member(s) (T1 and T2)may carry DC signals such as power and ground, a combination of both theDC level and a AC component could be used to supply power. Asillustrated in FIG. 13, a low frequency modulation may be imbedded uponthese signals so as to supply low data rate information.

Another example may utilize current modulation as illustrated in FIG.14. In FIG. 14, a current from a supply 1100 is fed through a currentmonitor 1110 prior to being sent over the tension member(s) (T1 and T2).At the other end, in parallel to a remote system 1130, a currentmodulator 1120 modulates the current in response to received data. Thecurrent modulator 1120 causes the modulation to be reflected back at thecurrent monitor 1110 so that the data corresponding to the modulationcan be captured.

In the various solutions discussed above, it is desirable to transmitthe data at a fixed data rate. The transfer of data at a fixed raterequires a circuit that will convert the variable rate data to a fixedrate. To convert from one data rate to another rate, some type of memorydevice is also needed. This allows data to be written into memoryelement at one rate then read out later at another rate. For example, aFIFO (first in—first out) type of memory element can be used.

As illustrated in FIG. 15, a data transmission system has a transmittercircuit at one end and a receiver circuit at the other end. In such agraphic system, the data into the transmitter can be at various ratesbased upon the users' requirements and the display's capabilities. Thegraphic resolution being used will determine the display system's pixelclock frequency. The transmitter converts, using a memory element 1200,the variable rate input to a fixed rate. The fixed rate data is sentacross some type of medium or channel to a receiver at the other end.The receiver receives the fixed rate data and stores the data into amemory element 1250. The data will need to be read out of the memoryelement 1250 at the same rate as data was read into the memory element1200 of the transmitter at the other end of the link.

However, the actual pixel clock from the transmitter is not sent alongwith the fixed rate data. The pixel clock at the receiver is notrecreated. The pixel clock at the receiver has to match thetransmitter's pixel clock or over time the memory may over-fill orunder-fill the memory element 1250.

More specifically, as illustrated in FIG. 15, if Z=X, the data enteringand leaving the system will be the same. On the other hand, if Z>X, thedata leaving the system will be faster than the data entering thesystem, this will cause memory element 1250 to request more data than isavailable, thereby creating an under-fill condition. Lastly, if Z<X, thedata leaving the system will be slower than the data entering thesystem, causing memory element 1250 to store excess data, therebycreating, over time, an over-fill condition.

The over-fill or under-fill conditions of the memory element 1250 willcause errors in the displayed image. Either there will not be enoughdata in memory element 1250 and data will be lost or too much data willbe in the memory element 1250 and not all of the image will bedisplayed. Since the receiver's clock rate will be very close to thetransmitter's clock rate, the errors will occur relatively slowly,basically causing the image to scroll.

Another way to avoid the memory storage issue on the receiver would beto transmit a reference clock. Implementing the extra clock signal willcreate extra noise, use an extra data channel and the fixed rate systemis not longer fixed rate. Also, to avoid the memory storage issue itcould be required to recreate the pixel clock at the receiver without anextra clock line. In this example, the transmitter is not required tosend a separate synchronous clock to the receiver for pixel clockalignment. A general protocol with counters, a clock synchronizer, in afeedback loop are used to determine the correct in pixel frequenciessuch that it will not cause a memory over-fill or an under-fillcondition and create an error free image.

As illustrated in FIG. 17, a data transmission system has a transmittercircuit at one end and a receiver circuit at the other end. In such agraphic system, the data into the transmitter can be at various ratesbased upon the users' requirements and the display's capabilities. Thegraphic resolution being used will determine the display system's pixelclock frequency.

The transmitter converts, using a memory element 1400, an unknown rateinput to a fixed rate. The fixed rate data is sent across some type ofmedium or channel to a receiver at the other end. The receiver receivesthe fixed rate data and stores the data into a memory element 1450. Thedata will need to be read out of the memory element 1250 at the sameunknown rate as data was read into the memory element 1400 of thetransmitter at the other end of the link.

However, the actual pixel clock from the transmitter is not sent alongwith the fixed rate data. The pixel clock at the receiver is notrecreated. The pixel clock at the receiver has to match thetransmitter's pixel clock or over time the memory may over-fill orunder-fill the memory element 1450.

At system power-up, the transmitter sends an estimate of the pixel clockfrequency. This is done by counting the number of clock transitions in agiven amount of time. As illustrated in FIG. 16, a counter 1300 countsthe number of pixel clock transitions between horizontal sync signals. Areference clock is also counted during the same. As illustrated in FIG.16, a counter 1350 counts the number of reference clock transitionsbetween horizontal sync signals. The pixel clock and the reference clockare not synchronous, nor are they integer multiples (they are notderived from the same clock source).

The non-synchronous clock will cause quantization errors in themeasurements. This is due to uncertainty of the two clock relationships(at any instant, the rising edge of the sampling clock could be at anyvarious relationship to the measured clock (before, after, or at thesame time)). Any time that the two are apart, the actual count is not awhole value, but a percentage. Since the round off is not an integer, ameasurement error will occur. The receiver also utilizes a knownreference frequency for measurements and clock re-creation. By using thereference clock along with the count value sent by the transmitter, aclose approximation of the pixel clock frequency can be obtained.

A digital clock synthesizer is used to re-create the receiver pixelclock frequency based on the percentage information that was sent in theprotocol. However, due to errors in the count value and rounding errorsduring the percentage calculation, the receiver's generated pixel clockfrequency will not be exactly the same as the transmitter's pixel clock.The error will cause over and under flow errors in the receiver's memoryelement 1500 of FIG. 18.

To determine a more accurate pixel clock frequency and avoid the underand overflow conditions, a control circuit is used to monitor thereceiver's memory usage. The control system provides information to thedigital clock synthesizer to alter the generated pixel clock frequency.A reference point in time is chosen that repeats at a constant interval.This reference point can be used as a guide to indicate the memory usagepatterns.

In this example, the horizontal frequency is used as a reference point.At each rising edge of the horizontal line signal, the amount of memorybeing used is stored. The measurement is done again on the nexthorizontal line signal edge. The location of the second measurement iscompared to the first measurement.

If the memory usage is increasing, the generated pixel clock is too slowand the digital synthesizer needs to increase the frequency. If thememory usage is decreasing, the digital clock synthesizer needs toreduce a frequency. This measurement feedback loop is in constantoperation; mainly due to the fact the digital synthesizer can neverrecreate the same frequency as the transmitter. Over time, thereceiver's pixel clock is at two different frequencies that are justabove and below the actual transmitted clock frequency. The average ofthe two values will be the same frequency as determined transmitter'spixel clock.

In the display example, the comparison is done once per line. If theamount of memory used in the memory element has changed with respect tothe previous time as illustrated in FIGS. 19 and 20 wherein FIG. 20illustrates an increase in usage since a previous time represented byFIG. 19, the previous horizontal line signal measurement, information issent to the digital synthesizer to either increase or decrease insynthesized frequency to more accurately match the transmitter's pixelclock. The system will assume that the digital synthesizer's pixel clockgeneration will never exactly match the transmitter's pixel clock. Toovercome this problem, the pixel clock will operate between twofrequencies, one just below the ideal frequency and one just above theideal frequency. Over time, the average value will be the same frequencyas a transmitter's pixel clock.

At system power-up, the two frequencies of operations will have arelatively large difference. As a system operates, the differencebetween the two frequencies will be reduce. This will continue until thedifference is below any errors that may occur by operating at onefrequency at extended lengths of time. For system robustness overenvironmental all changes, additional monitors can be used to re-adjustthe two frequencies if needed.

As noted above, Digital Visual Interface and/or High-DefinitionMultimedia Interface are graphic protocols that send graphic data andcontrol data from a source 1800 of FIG. 21 to a display 1850 of FIG. 21.Control information is also sent from the display to the source 1800.The graphic information is at high data rate, while the controlinformation is at low data rate. Since control data is flowing in bothdirections, the system requires some type of bi-directional link. Sincethe return control data is not constant, when control data is beingsent, the data rate is slow relative to the graphic data from the sourceto the display. The return control data is only active a very smallpercentage of the time relative to the downstream graphic data.

One approach to creating such a bi-directional link is illustrated inFIGS. 22 and 23. This approach takes advantage of how the Digital VisualInterface and/or High-Definition Multimedia Interface protocol isdefined. Since Digital Visual Interface and/or High-DefinitionMultimedia Interface is a graphic interface, it has data periods as wellas non-data periods. The non-data periods are at the end of each line ofdata, prior to the next horizontal sync signal. There is also non-datatime after all of the lines have been sent to the display, prior to thenext vertical sync signal.

The approach provides bi-directional data without requiring two separatechannels by applying time multiplexing between the source and display.The source to display transmission can be stopped when display data orcontrol data is not being sent, then information from the display to thesource can be sent using the switching architecture illustrated in FIG.23.

As illustrated in FIG. 23, a source 2000 prepares graphic data andtiming information to be sent to a display 2400. When the source 2000 issending graphic data and timing information to be sent to the display2400 over communication channel 2200, switching circuit 2100 isconfigured so that data flows from the source 2000 to the display 2400.Moreover, switching circuit 2300 is configured so that data flows fromthe source 2000 to the display 2400 when the source 2000 is sendinggraphic data and timing information to be sent to the display 2400 overcommunication channel 2200.

On the other hand, when the source 2000 is not sending graphic data andtiming information to be sent to the display 2400 over communicationchannel 2200, switching circuit 2100 is configured so that data flows tothe source 2000 from the display 2400. Moreover, switching circuit 2300is configured so that data flows to the source 2000 from the display2400 when the source 2000 is not sending graphic data and timinginformation to be sent to the display 2400 over communication channel2200.

It is noted that the various embodiments described above can be utilizedin a remote workstation/central processing environment as illustrated inFIG. 24. In this environment, as illustrated in FIG. 24, a centralcomputing facility or room 3000 contains all of the primary processingcapability for each user in the form of “Blade PCs.” A Blade PC is theprimary processing center for a user of the system such that each useris assigned and connected to an individual Blade PC. In other words, theBlade PC would be equivalent to the user's actual personal computer in adistributive system.

The remote workstation/central processing environment enables theprimary processing facility to be located in a temperature controlledenvironment. Moreover, the remote workstation/central processingenvironment enables the elimination of individual PC cases, allows for acommon power supply, and reduces the machine noise in the user'senvironment.

As further illustrated in FIG. 24, each user has, at their station ordesk (3300, 3400, or 3500), a monitor (3340, 3440, or 3540); an inputdevice (3320, 3420, or 3520) such as a keyboard, pointing device (mouse,digital pad, and/or light pen) and/or microphone, etc.; and/or an inputand/or output device (3330, 3430, or 3530), such as a storage device (CDR/W Drive, DVD R/W Drive, floppy drive, and/or removable memory device),speakers, docketing station, and/or digital imager, etc. Each stationalso includes an interface (3310, 3410, or 3510) that provides a bridgebetween the station's devices and the associated optical communicationlink (3200, 3210, or 3220).

The various communication links are connected to an interface 3100 atthe central computing facility 3000 so that each Blade PC has an opticalcommunication link to an associated station. The optical communicationlinks (3200, 3210, or 3220) carry not only graphical data from the BladePC to the associated station, but also carries all the data between theBlade PC and the various associated station devices; i.e., datagenerated by a keyboard or a mouse. This communication of data may bebi-directional.

To facilitate proper communication between the central computingfacility 3000 and each station (3300, 3400, or 3500), the interfaces(3310, 3410, or 3510) would include the various components, as describedabove, that facilitate optical to electrical and electrical to opticalconversions. More specifically, in one possible embodiment of thepresent invention, the interface 3100 would measure the various timingsignals to generate timing information wherein the timing information isfed to a programmable gate array.

The programmable gate array produces the header information from thetiming information and encodes the multiple channels of graphic data;e.g., red, green and blue channels of data. The programmable gate arrayfurther transmits the header information with the graphic data and theappropriate idle codes, when necessary, to a digital to opticalconverter. The digital to optical converter converts the data to astream of lights pulses. The light pulses are fed to an opticaltransceiver to be transmitted over one of the optical communicationlinks (3200, 3210, or 3220) which transmits the data to the appropriatestation (3300, 3400, or 3500).

At the station end, the interfaces (3310, 3410, or 3510) would includean optical transceiver that receives the light pulses from the opticalcommunication links (3200, 3210, or 3220). The light pulses areconverted to electrical signals by optical to digital converter. Thefixed data rate electrical data stream is decoded by programmable gatearray to produce graphic data and timing information. The timinginformation is converted into timing signals. The timing signals and thedecoded graphic data are fed to the monitor or display device (3340,3440, or 3540).

As noted above, the system sends data back and forth from point A topoint B; however, the system does not send the same amount of data inone direction as in the other direction. More specifically, in theconventional system, Point A could be sending data at 2 Gb/s to point B,but Point B is only sending 1 Mb/s of data to Point A. Typically, thistype of system would require two fiber channels, one for the high speeddownstream data and one for low speed upstream data, or a single modesystem that creates bi-directional data stream with two differentwavelengths, which adds additional circuitry.

To avoid the above-noted problems, as noted above, a solution may be touse an optical fiber to send the high rate data to Point B from Point A,but use an electrical signal caring medium for the data transfer fromPoint B to Point A. For example, a fiber assembly may contain bothoptical fibers for high data rate signals and a tension member(s) thatare designed with a low resistance material. The tension member(s) canbe used to carry the lower data rate electrical signals.

There are various ways that the electrical signal could be constructedon the tension member(s). The tension member(s) may carry DC signalssuch as power and ground, a combination of both the DC level and an ACcomponent could be used to supply power. A low frequency modulation maybe imbedded upon these signals so as to supply low data rateinformation. Another example may utilize current modulation as discussedabove.

It is noted that any data from the display to the source can be held inmemory until one of the idle times is present. Then the return data canbe sent on the same channel. It is also noted that various othertechniques at each end of the channel can be developed to handle boththe transmission and receiving of data at each termination point.

While various examples and embodiments of the present invention havebeen shown and described, it will be appreciated by those skilled in theart that the spirit and scope of the present invention are not limitedto the specific description and drawings herein, but extend to variousmodifications and changes.

1. A point-to-point communication cable, comprising: a first interfacehaving first and second communication members to provide communicationchannels; a second interface having third and fourth communicationmembers to provide communication channels; an optical fiber, operativelyconnected to said first communication member of said first interface andsaid third communication member of said second interface, to provide acommunication channel between said first interface and said secondinterface; a sheath, surrounding said optical fiber, to protect saidoptical fiber; and a tension member, located within said sheath, toprovide tensile stiffness for said optical fiber; said tension memberbeing operatively connected to said second communication member of saidfirst interface and said fourth communication member of said secondinterface; said tension member providing an electrical path between saidsecond communication member of said first interface and said fourthcommunication member of said second interface.
 2. The point-to-pointcommunication cable as claimed in claim 1, wherein said tension memberis composed of a low resistance material.
 3. The point-to-pointcommunication cable as claimed in claim 1, wherein said optical fiberprovides a communication channel for transmitting at a rate greater thana gigabit/second.
 4. The point-to-point communication cable as claimedin claim 1, wherein said tension member provides a communication channelfor transmitting at a rate less than a megabit/second.
 5. Thepoint-to-point communication cable as claimed in claim 3, wherein saidtension member provides a communication channel for transmitting at arate less than a megabit/second.
 6. The point-to-point communicationcable as claimed in claim 1, wherein said tension member carries a DCsignal.
 7. The point-to-point communication cable as claimed in claim 1,wherein said tension member carries DC and AC signals to provide powerand low data rate information.
 8. The point-to-point communication cableas claimed in claim 1, further comprising: a spacer housed in a spaceencircled by said sheath.
 9. The point-to-point communication cable asclaimed in claim 8, wherein said spacer includes an axial portion and aplurality of partitioning plate portions.
 10. The point-to-pointcommunication cable as claimed in claim 9, wherein said spacer has asectional shape such that said partitioning plate portions radiallyextend toward an inner circumferential surface of the sheath from saidaxial portion.
 11. The point-to-point communication cable as claimed inclaim 1, wherein said second and fourth communication members aremetallic pins.
 12. The point-to-point communication cable as claimed inclaim 1, wherein said second and fourth communication members aremetallic sockets.
 13. A communication system for providing a transfer ofdata between two devices, comprising: a point-to-point communicationcable; said point-to-point communication cable including, a firstinterface having first and second communication members to providecommunication channels, a second interface having third and fourthcommunication members to provide communication channels, an opticalfiber, operatively connected to said first communication member of saidfirst interface and said third communication member of said secondinterface, to provide a communication channel between said firstinterface and said second interface, a sheath, surrounding said opticalfiber, to protect said optical fiber, and a first tension member,located within said sheath, to provide tensile stiffness for saidoptical fiber, said first tension member, operatively connected to saidsecond communication member of said first interface and said fourthcommunication member of said second interface, providing an electricalpath between said first interface and said second interface, a currentsource, operatively connected to said second communication member, toprovide a current onto said first tension member; a switch, operativelyconnected to said fourth communication member, to modulate the currentflowing through said first tension member in response to data generatedby a device connected to said second interface; and a current monitor,operatively connected to said second communication member, to monitorthe modulated current and to generate a data signal in response thereto.14. The communication system as claimed in claim 13, wherein saidtension member is composed of a low resistance material.
 15. Thecommunication system as claimed in claim 13, wherein said optical fiberprovides a communication channel for transmitting at a rate greater thana gigabit/second.
 16. The communication system as claimed in claim 13,wherein said tension member provides a communication channel fortransmitting at a rate less than a megabit/second.
 17. The communicationsystem as claimed in claim 16, wherein said tension member provides acommunication channel for transmitting at a rate less than amegabit/second.
 18. The communication system as claimed in claim 13,wherein said tension member carries a DC signal.
 19. The communicationsystem as claimed in claim 13, wherein said second and fourthcommunication members are metallic pins.
 20. The communication system asclaimed in claim 13, wherein said second and fourth communicationmembers are metallic sockets.